Maybe you’ve heard of the USB killer, a $49 device that you plug in and fires a surge of power through your computer’s motherboard if it’s not isolated well enough — which is often the case.

DIY YouTuber named Thomas Kim has shown it’s not that hard to create something that has the same effect yourself. By combining camera flash parts with a AA battery, the device delivers 300 volts when plugged into an unsuspecting computer. It’s effectively the same as a power surge, but the difference is that most power supplies have protection against those. USB buses often can’t offer the same kind of resistance, and consequently relay the energy to the rest of the computer, instantly killing it.